Replacing with "opaque box"

[marktab]

Per https://docs.microsoft.com/en-us/style-guide/a-z-word-list-term-collections/b/black-box replacing with "opaque box"

[PRMerger10]

@marktab : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[PRMerger18]

@rothja : Thanks for your contribution! The author(s) have been notified to review your proposed change.

[rothja]

@marktab Thank you! #sign-off

[PRMerger18]

@rothja: I'm sorry - only the author of this article, @s-r-k, can sign off on your changes. But we do have an exception process - if you are on the Microsoft content or product team for this product area, you can ask the PR review team to review and merge it by sending mail to the techdocprs alias.